Heritable, biologically important differences in perception and motor behavior that do not result from exposure to different environments are well-documented among closely-related species of most higher vertebrates, yet little is known about the changes in nervous systems which contribute to these species differences. The present research plan examines the cellular correlates of species behavioral differences. Transplants of defined portions of central nervous system tissue between the embryos of two gallinaceous birds, the Japanese quail (Coturnix japonica) and the domestic chicken (Gallus domestricus) are performed at early stages of development and transplanted host embryos are allowed to hatch. The resulting animals, called chimeras, have selected central nervous system (CNS) regions made up from cells of the donor species. Donor and host regions of he CNS can be verified in subsequent histological examination using as previously-discovered species-specific nuclear cell marker. Preliminary work shows that chimeras with transplants of small brain regions or even a majority of the brain can hatch, that such chimeras can survive long enough to permit behavioral studies, that the species-specific cell marker remains identifiable in hatched animals, and that aspects of one stereotyped vocal behavior ("crowing") characteristic of the donor species can be transplanted to the host species with transplants of portions of the presumptive brain. In the work proposed here, transplants will be used to address the question of whether all aspects of this behavioral difference are central in origin, and to map out which CNS regions controlling crowing are responsible for the species differences. At the same time, the neural pathways involved in crowing will be traced in normal animals. The development of these and other CNS regions will also be examined in both species, using a combination of the quail-chick marker and a retroviral cell lineage marker technique. Such novel information on the relationship between brain structure, brain development, and the neural control of behavioral function, as well as the morphological and behavioral effects of CNS transplant could be useful for the understanding of neural defects, and may provide new insights into possible clinical intervention via neural transplantation.